Not Displaying Background

i hav a fixed width theme in which content division contains the psot and sidebar.

<div id=”content”>
<div id=”content-left”>
</div>
<div id=”content-right”>
</div>
</div>

i hav set a background in content and repeat it on y axis.
but the problem is that whenever i flot content-left to left and content-right to right background get disappear.

here is the css

#content {
background: transparent url(‘images/bg_middle.jpg’) repeat-y;
}
#content-left {
margin: 0px 10px 0px 20px;
width: 65%;
float: left;
}
#content-right {
margin: 0px 20px 0px 10px;
width: 28%;
float: right;
}

this remain untill i hav not put this

#content {
background: transparent url(‘images/bg_middle.jpg’) repeat-y;
float: left;
width: 100%;
}

whats the reason.